Table Of ContentNotes ichtyologiques / Ichthyological notes
First report of a totally ambicoloured Patagonian
flounder Paralichthys patagonicus (Paralichthyidae)
with dorsal fin anomalies
by
Juan M. DÍAZ DE ASTARLOA (1), Rita RICO (2) & Marcelo ACHA (1, 2)
RÉSUMÉ. - Premier signalement d’un Paralichthys patagonicus RESULTS
totalement ambicoloré, avec des anomalies de la nageoire dorsale.
The flatfish has the typical pigmentation developed on the ocu-
L’exemplaire, capturé dans les eaux des côtes d’Argentine au
lar side characteristic for the species. It differs from other speci-
large de Necochea (38º37’S-58º50’W), est entièrement ambicoloré,
mens in that it is also virtually totally pigmented on the blind side
et présente aussi un développement anormal de la nageoire dorsale
et une migration incomplète de l’œil droit. Il s’agit ici du troisième (Fig. 1A). The entire blind (right) side is uniformly dark brown,
signalement du phénomène d’ambicoloration chez une espèce de
Paralichthys dans l’Atlantique sud-ouest.
Key words. - Paralichthyidae - Paralichthys patagonicus - ASW -
Argentine coast - Ambicoloration - Head anomalies.
A typical anomaly of flatfishes is malpigmentation, which is
characterized by either a deficiency of pigment cells on portions of
the ocular side (albinism, pesudoalbinism, or hypomelanism), or
the presence of dark pigmentation on the normally light-coloured
underside of the fish, also called ambicoloration (Bolker and Hill,
2000).
In May 2003, one totally ambicoloured and anomalous speci-
men of the Patagonian flounder Paralichthys patagonicus Jordan,
in Jordan and Goss, 1889 was caught by a commercial bottom-
trawler off Necochea (38°37’S-58°50’W), Argentina, at 31 m
depth. Paralichthys patagonicus is one of seven paralichthyid
flounders known from southwestern Atlantic waters (Díaz de
Astarloa, 1994). This moderate to large-sized flounder (females to
ca. 640 mm in standard length [SL]) is a common inhabitant in
nearshore and offshore waters of northern Argentina (38°-41°S),
and is the most economically important paralichthyid flounder in
the southwest Atlantic (Díaz de Astarloa, 2002).
The specimen was identified, measured to the nearest 1 mm SL
with an ichthyometre and a calliper, photographed with a Nikon
Coolpix 4500 digital camera, fixed in 10% buffered formalin, pre-
served in 75% industrial ethylated spirit and housed in the fish col-
lection of the Instituto Nacional de Investigación y Desarrollo Pes-
quero as INIDEP 726. The aberrant specimen was x-rayed to deter-
mine presence and extent of osteological abnorm alities.
Counts and measurements were made on the wholly ambi-
coloured specimen for comparison with those of normal coloration.
Figure 1. - Totally ambicoloured Patagonian flounder, Paralichthys patago-
The only unusual measurement noted for this specimen was a much
nicus, 334 mm SL, taken off Necochea, Argentina. A: Blind side; B: Ocular
larger predorsal length. Otherwise, counts and morphometric fea- side. (Photograph by M. R. Rico). [Cardeau patagonien, Paralichthys
tures were well within ranges recorded for the species (Díaz de patagonicus, entièrement ambicoloré, capturé au large de Necochea, Argen-
Astarloa, 1994). tine. A : Face aveugle ; B : Face oculée.]
(1) Departamento de Ciencias Marinas, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Consejo
Nacional de Investigaciones Científicas y Técnicas (CONICET), Funes 3350, B7602AYL Mar del Plata, ARGENTINA.
[[email protected]]
(2) Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), Paseo Victoria Ocampo s/n, B7602HSB Mar del Plata,
ARGENTINA.
Cybium 2006, 30(1): 73-76.
Ambicoloration in Paralichthys patagonicus Díaz De astarloa et al.
except for a triangle-shaped unpigmented patch near the base of
caudal-fin rays, but otherwise its coloration resembles that of the
ocular (left) side.
Externally, obvious morphological deformity is evident in the
cranial region of the head. The Patagonian flounder has an anoma-
lous development of a fleshy hook at the anterior end of the dorsal
fin and it also features incomplete migration of the right eye. Instead
of being situated on the medial region of the head, as it is typical
for other specimens, the right eye of this specimen migrated only as
far as the dorsal crest under the fleshy hook formed as a result of
the obstructed forward growth of the dorsal fin. In this position it is
visible from the right side (Fig. 1A), which is not typical of this
species. Additionally, unlike normal specimens in which predorsal
length (snout to dorsal fin origin) ranges from 3.4-6.5% SL, in this
totally ambicoloured specimen the predorsal length is much longer
(10.3% in SL). Further differences are that the blind-side skin
resembles in some aspects that normally seen on the ocular side. In
non-ambicoloured specimens the ocular-side scales are ctenoid and
those on the blind side are cycloid. The posterior part of the ocular-
side maxilla is covered by scales, while that on the blind side is
scaleless. The anus opens on the blind side and the urogenital papil-
la is located on the ocular side forward and dorsal to the first anal
fin ray. In contrast, the ambicoloured specimen has distinctly
ctenoid scales on the blind side, the anus opens on the ocular side,
slightly above the anal fin origin, while the urogenital papilla is
located on the blind side, and the posterior part of the maxilla is
scaly.
Examination of a radiograph of this specimen (Fig. 2A) clearly
shows the incomplete development of the dorsal fin over the skull.
Whereas in normal specimens (Fig. 2B) the dorsal fin origin devel-
ops over the anteriormost part of the neurocranium, in the totally
ambicoloured specimen, the dorsal fin origin appears only over the
posterior third of the neurocranium, near the occipital region (Fig.
2A). This abnormal position is reflected in the much larger predor-
sal length of this specimen compared to that of non-anomalous
specimens. In the anomalous specimen there is also a vertical pro-
cess developed in the middle part of the skull (Fig. 2A). This pro-
cess appears to support the fleshy hook of the dorsal fin.
DISCUSSION
Flatfish specimens have been recorded as being total (Gudger,
1941, Haaker and Lane, 1973), almost total (Gudger and Firth,
1935; Gudger, 1936; Forrester and Smith, 1971; Fujita, 1980; Díaz
de Astarloa, 1995, 1998), or partially ambicoloured (Gudger and
Firth, 1936; Okiyama and Tomi, 1970; Wilkens and Lewis, 1971;
Love and Vucci, 1973; Taylor et al., 1973; Stickney and White,
1975; Díaz de Astarloa, 1995). Previous reports of ambicoloured
flatfishes are those of species occurring mainly in northwestern
Atlantic and eastern Pacific waters. Dawson (1962) recorded an
incompletely ambicolorate specimen of Paralichthys lethostigma
trawled in Calibogue Sound, South Carolina, and an almost total Figure 2. - A: Radiograph of head of aberrant Paralichthys patagonicus
ambicoloured specimen of Trinectes maculatus collected in the (334 mm SL) showing incomplete formation of dorsal fin. B: Radiograph of
estuary of the Caloosahatchee River, Florida. Six ocellated floun- head of a normal Paralichthys patagonicus (405 mm SL). VP: vertical pro-
cess; DFR1: first dorsal-fin ray. [A : Radiographie de la tête d’un individu
ders, Ancylopsetta quadrocellata, with pigmented blind sides were
aberrant montrant la formation incomplète de la nageoire dorsale. B :
taken in the lower Newport River estuary, North Carolina (Wilkens
Radiographie de la tête d’un individu normal. VP : processus vertical ;
and Lewis, 1971). Other ambicoloured flatfishes are a partially
DFR1 : premier rayon de la nageoire dorsale.]
ambicolorate fringed flounder, Etropus crossotus, captured from
coastal waters of Georgia (Taylor et al., 1973), a totally ambi- pletely ambicoloured specimen with skeletal anomalies of Petral
coloured specimen of Paralichthys californicus collected in Ana- sole, Eopsetta jordani, taken off the west coast of Vancouver Island
heim Bay, California (Haaker and Lane, 1973), and an almost com- (Forrester and Smith, 1971).
74 Cybium 2006, 30(1)
Díaz De astarloa et al. Ambicoloration in Paralichthys patagonicus
Ambicoloration occurs frequently in hatchery-reared flatfish. totally ambicoloured Hypsopsetta guttulata with a depression
Specimens with nearly 100% ambicoloration have been observed formed in the frontal region of the head. Fujita (1980) found a
in tank cultured Paralichthys dentatus (L.) and P. lethostigma Jor- reversed almost completely ambicolorate Platichthys bicoloratus
dan & Gilbert (Stickney and White, 1975), and 95% of hatchery- (cited as Kareius bicoloratus) with a fleshy hook developed on the
reared Japanese flounder (Paralichthys olivaceus) populations anterior edge of the dorsal fin.
showed black areas on the underside of body (Tominaga and The abnormal flatfish specimen reported in the present study
Watanabe, 1998). Houde (1971) found high abnormality frequen- represents the first documented occurrence of a totally ambi-
cies (up to 84%) in laboratory-reared lined soles Achirus lineatus. coloured Paralichthys patagonicus with an incomplete eye migra-
Blind-side pigmentation is uncommon in wild. Three Califor- tion and hooked anterior dorsal fin, and the third record of ambicol-
nia halibut specimens, P. californicus, from a total of 1,256 have oration in a species of Paralichthys occurring in southwestern
been reported to have ambicoloration (Haaker and Lane, 1973), and Atlantic region.
although this defect has no pathogenic effect on the fish, chances of
survival in the wild are greatly reduced (Koshiishi et al., 1991).
Frequencies of anomalies in various groups of flatfishes were
Acknowledgments. - The authors are much indebted to A. Bianca and M.
thought to occur more frequently in less specialized flatfishes, such
Sosa (observers Instituto Nacional de Investigación y Desarrollo Pesquero,
as paralichthyids and pleuronectids, and less frequently in more
Argentina) for donating the abnormal specimen, and to T.A. Munroe
derived groups including the soleids and cynoglossids (Gartner,
(National Marine Fisheries, National Museum of Natural History, Washing-
1986). Whereas ambicoloration is well documented and apparently ton, D.C., USA) and L.O. Lucifora (Consejo Nacional de Investigaciones
rather common in the Bothidae and Pleuronectidae, few records Científicas y Técnicas, Argentina) for providing critical literature. E.A.
report such anomalies in the species of Achiridae, Soleidae and Aristizabal (Instituto Nacional de Investigación y Desarrollo Pesquero,
Cynoglossidae. Dawson (1962), summarizing results from the lit- Argentina) kindly took the radiograph.
erature, listed 27 specimens of bothids and pleuronectids showing
four types of ambicoloration, but noted only two cases of abnormal
coloration in the other families including an almost completely
ambicolorate Trinectes maculatus (Achiridae) and a partially ambi-
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Reçu le 23 août 2004.
Accepté pour publication le 16 février 2005.
76 Cybium 2006, 30(1)
